The invention relates generally to apparatus for absorbing and dissipating the impact energy of automobiles or other moving vehicles. More particularly, the invention relates to an end treatment for a guardrail which will redirect the nose of the impacting vehicle away from the unyielding guardrail while at the same time dissipate the energy of an impacting vehicle.
Rigid guardrails are usually positioned alongside vehicular traffic routes, especially highways, for the purposes of preventing vehicles from colliding with fixed objects, other vehicles or driving off the road. To this end, the guardrails must be rigid enough to prevent the lateral movement of an impacting vehicle. While guardrails function to prevent vehicles from impacting unyielding objects they themselves present a hazard to a vehicle which might impact the end portion of the unyielding guardrail.
Energy attenuation and absorbing devices for highway abutments are known in the art. An example of such a unit is U.S. Pat. No. 4,352,484 to Gertz, et al. These devices are utilized to dissipate the impact energy of a vehicle. To this end, these barriers usually include a deformable structure or material which dissipates the energy of an impacting vehicle as it is crushed. Despite the success of these devices they are typically too expensive to be used to prevent vehicles from impacting guardrails.
Highway barriers have been developed for use with the end portions of guardrails. An example of these prior art devices are fender panels which are designed to telescope upon the application of an axial impact force. These prior guardrail barriers typically have difficulties dissipating the energy of large vehicles or vehicles traveling at high speeds. When these devices are impacted at high speeds, the fastening members are sometimes pulled through the panels causing the panels to separate and failing to telescope. Furthermore, if the telescoping panels do not dissipate a sufficient amount of the energy the impacting vehicle will hit the unyielding portion of the guardrail after the panels have telescoped. This can result in the fender panels of the guardrail spearing the car and seriously injuring its occupants.
Breakaway cable terminals are also used to dissipate the energy of a vehicle impacting the end portion of the guardrail. Basically, a breakaway cable terminal is a cable which extends from the first vertical support leg to a fender panel at a position in front of the second vertical support leg. Upon impact, the first vertical leg is designed to breakaway releasing the cable and minimizing the spearing forces. This design though has had difficulty in preventing light weight vehicles travelling at high speeds from being speared by a fender panel upon axial impact of the guardrail.